So I was simply copying an entire photo folder from one of my external HD's to another external HD, when the connection was interrupted due to the main ext HD's USB plug being removed. *don't ask*

It was about 100 gigs into the transfer of about 130 gigs in total, and now I have no idea of where to start transferring from again, since OS X doesn't just copy everything without duplicating what's already there.. it simply asks if you want to over wright or not, and only single files at a time. *WHY is that by the way ? what a silly thing!*

I was planning on looking for software to scan and synchronize my external HD's anyway, so at this point I'd like to kill two birds with one stone if possible. Can anyone recommend something to cure my current ail ?